Chamberlain said he estimates the officer was about 50 to 75 yards away when he fired.

Officers rarely fire shots in the prison, he said, but are authorized to do so under certain conditions, such as when there is a "likelihood of death."

"In this case, the inmate was knocked unconscious and was unable to defend himself," he said.

The officer has been assigned to work in another part of the prison while the shooting is reviewed, he said. The state Inspector General's Office was notified Friday.

"Any time lethal munitions are fired, the officer is redirected to another assignment," he said.

The man regained consciousness and was treated at the prison's infirmary.

The prison was placed on lockdown on Friday while officers complete their investigations, including looking into whether the incident was gang-related.

C facility houses gang members, among others.

Chamberlain said Espinoza is serving 18 years to life from Kern County for first-degree murder. Pineda is serving 25 years-to-life for second-degree murder and attempted second-degree murder in Riverside County.

Chamberlain said Espinoza has been incarcerated for about 23 years.

After the prison's investigation is done, Chamberlain said, officials there will file criminal charges against Espinoza and Pineda with the Monterey County District Attorney's Office.